Power transmission apparatus



Dec. 26, 1950 HOBBS 2,535,924

POWER TRANSMISSION APPARATUS Filed July 5, 1946 4 Sheets-Sheet 1 Int 8177221:

Dec. 26, 1950 H. F. HOBBS 4 POWER TRANSMISSION APPARATUS Filed July s, 1946 4 Sheets-Sheet 2 [45 7 36 52 J I 4 40 5/ G E a 12.32% 44 5 I 4 I :9 a 5 l5 Inventor H. F fralrs Dec" 26, 1950 H. F. HOBBS POWER TRANSMISSION APPARATUS 4 Sheets-Sheet 15 Filed July 5, 946

m w 2 z 3 y 50%??? E z g 4% 1 g g0 2 Dec. 26, 1950 1-1. F. HOBBS ,9

POWER TRANSMISSION APPARATUS Filed July 3, 1946 4 Sheets-Sheet 4 fnl evzfor HF H0553 Patented Dec. 26, 1950 POWER TRANSMISSION APPARATUS Howard Frederick Hobbs, Leamington. Spa, England, assignor to Hobbs Transmission Limited Application July 3, 1946; Serial No. 681,321 In Great Britain July 9, 1945 9 Claims. (Cl. 74-330) This invention'relates to power transmissio apparatus of the kind having at least two hydraulically actuated clutches provided with movable clutch engaging rings carried by a rotary part and spaces to receive fluid under pressure for actuating said rings and inlet and exhaust ports associated with said spaces and controllable by valve means.

The main object of the present invention is to provide an apparatus of this kind with valve device (or more than one) having a, centrifugally movable piston and adapted for automatically changing drive from one clutch to another at suitable predetermined speeds of the rotary part, the speed at which said piston moves outwards being different from that at which it moves inwards.

Another object of the present invention is to provide a means whereby the operator can vary the operation of said device to cause it to effect change of ratio at different speeds.

According to the present invention an apparatus of the kind referred to is provided with at least one valve device carried by said rotary part which device has a valve piston which'is held inwards by spring means and operated outwardly by centrifugal force, a spring pressed element also carried by said rotary part and acting on said valve piston to locate it in positions at the ends of its travel, ports being provided which are controlled by said piston for filling and exhausting the fluid spaces of the clutches whereby the clutches are engaged or disengaged when said piston is located in each of the twopositions.

The provision of a spring pressed element in addition to the spring pressed and centrifugally operated piston ensures that the apparatus can be brought into only one or other of the aforesaid definite positions and the location of the exhaust ports and/or channels ensures permanent and complete exhausting of the fluid from a clutch or filling when required.

The change from one condition to another will occur at a predetermined degree of the centrifugal force on the piston, and consequently at a predetermined speed of the aforesaid rotary part, but. the degree of force required for outward movement is more than that required for the inward movement of the valve piston.

The spring pressed element may consist of a outwards at a greater speed of the said rotary part than the speed at which the piston moves inwards. Engagement of the appropriate clutches at difierent driving periods to bring difierent ratios into operation results in variation in the speeds of the rotary part, and the difference in the speeds required for outward and inward movements of the piston should be greater than the difierence in speeds caused by the change in transmission ratio. This effect is achieved by using the aforesaid spring pressed detent and selecting the mass of the piston, the strength of it is necessary to ensure that the piston will move plate I! is mounted directly on the shaft 30.

shaft 29 comprises also the mainshaft of the the spring means operating on the piston, and the resistance against movement of the piston provided by the detent. Means may be provided whereby the operator can vary the speeds at which the said piston or pistons will change from one position to another.

The invention will now be described by way of example with reference to the accompanying drawings wherein- Figure l 1 is a vertical sectional view of an apparatus made in accordance with the invention;

Figure 2 is a sectional view on the line A-A on Figure 1;

Figure 3 is a view partly in section on the line B-B on Figure 1;

Figure 4 is a sectional view illustrating a modified construction of part of the apparatus; and

Figure 5 is a sectionalview of a gearbox used with the said apparatus.

Referring first to Figures 1, 2, 3 and 5 the input shaft or engine crankshaft 10 carries the rotary part which takes the form of a housing comprising a front plate 1 I, rear plate H2, rings H3, H4 and drum H5. This housing contains and carries two clutch pressure rings l3, [4 which are pressed apart for clutch disengagement by springs I it, and two flexible diaphragms l8, I9, to one side of each of which is a, space to which oil under pressure can be admitted whereby the pressure rings l3, It are caused to engage friction clutch plates l6, ll, respectively.

The clutch plate I6 is mounted on the cage 25 of a differential gear, the crown wheels 26, 21, of which are mounted respectively on two concentric intermediate shafts 29, 3B. The clutch The gearbox and the output shaft of the apparatus. The intermediate shaft 38) carries a gearwheel 35 (Figure 5) in mesh with a gearwheel 37. mounted on a layshaft'38; The layshaft 38 also carries another fixed gearwheel 4| in permanent mesh =to its axis.

The oil to the spaces associated with the .dia

phragms is supplied by a pump 23 through a port 2i and suitable ducts such as 653 is a relief valve for the pump.

The supply of oil is controlled automatically for producing the required ratios by suitable valves. Two of these valves comprise the valve piston '8 '-:and an additional valve piston 9 slidable in bores drilled in the housing plate H2 at right angles These valves serve for automatically changing drive from one clutch to another at a predetermined speed of the rotary housing ll. Oil under pressure from the pump 2d reaches a --'port 2 via a duct .3! and is led to the inner .end

The 'valve piston 8 is 1.1'

of the bore of the valve 3. "urged inwards by a spring 132 which acts between "jthe base of the valve piston and a'pin 33 which abuts against a plug 3:3 which is screwed into the mouth of the bore and has exhaust holes 33. "'The valve piston '3 is urged inwards by a spring iii, which acts between the base of the piston and a plug iSi which has exhaust holes 5 23.

The valve piston 8 has an opening t lt in its "inner end through which oil reaches the interior .of the piston. The piston '8 is provided with an annular port 45 at its outer end which port is in -"'constant communication through aduct H55 with "the interior of the piston. The valve piston t port E56.

With the pistons 8 and 9 in the positions shown "the oil pressure 'is led through port duct e5,

port dl, in valve 9 and ducts the to the diaphragm 19, and the diaphragm it is open to exhaus 'hrough duct 2 and holes 8.

At some given rotary speed of the housing ii the piston 3 will be in its inwards position and the apparatus will operate in the first ratio. The force from the spring 32 may be in excess of the centrifugal force tending to move the piston outwards. I-

rotary speed of the housing ii is suitably increased, the centrifugal force on the piston becomes sufiicient to overcome the force from the spring, but the piston will not move out wards until the speed is still further increased and the centrifugal force increases suficienty to overcome both the force from the spring 32 and the resistance of the ball 36 in the groove 4d. The piston will then move outwards and it abuts against the screwed plug .34 :in which position pressure is led from the port it to the diaphragm is, via the duct 24. The diaphragm 19 will exhaust through the ports and ducts, I54, 41, t6, and 55B. This causes a change in driving ratio, i, e. from first to second and unless the vehicle, or other driven machine, changes its speed, the rotary speed of the housing I I will vary in accordance with the change in driving ratio. If 'itwere not for the balldetenttt groove 48 spring ii), the reduction in rotary speed would cause the piston 8 to move inwards and cause a change back to first ratio. The spring Ail ball 35 and groove s4 are so designed that the restraining force, relative to the centrifugal force on the piston and the force from the spring 32 is such that a still greater change in the rotary speed of the-housing is required before the piston will move inwards.

When in the outward position, a suitable decrease in speed, whichwill be greater than that necessitated by change of one ratio to the next, will cause the force from the spring :32 to be SL iently in excess of the centrifugal force on the piston 8 to overcome the resistance of the ball 36 and the groove 43, and the piston will return to its :inner position where it abuts against the inner end of the cylindrical bore in which it operates. The change of drive ratio fromsecond to first will cause some predetermined maximum increase in rotary speed of the housing H but theginorease inspeed required 'to cause the piston to move outwards will be greater than this increase caused by change .in ratio.

Variation of the strength of the spring as, the mass of the piston is and spring 32 remaining the same, will cause the difference in the speeds required for outwards and inwards movement to be varied.

The pressed ball serves to assist positioning in either the inner or outer position and to produce :a suitable resistance to the valve piston 8.

The mass of the piston 6, the strength of the spring 532., and theresistance of the spring pressed ball 35, are so selected that the piston will move outwards at a greater speed oi the housing I! than the speed at which the piston moves in- Wards and that the difierence in the speeds required for outward and inwards movements will be greater than the difiference in speeds caused by :the change in transmission ratio.

An apparatus constructed according to their-i vention may comprise only the valve 8 which will serve to cause engagement of either clutch :5 or ll. However, the apparatus being described provides three ratios and, the first is obtained with clutch Ill engaged and the second with clutch whilst the third operates when both i! and l 6 are engaged together. The purpose of the valve 3 is to cause pressure to be supplied to both H3 and fl together. In operation the valve 2 is similar to the valve 8 and the valve pistons are interlocked by the balls 49 and grooves 5d,.5l. With the valve pistons 8, '9, in th inner positions the balls 59 are moved to engage the groove 5!. Hence the valve piston 8 cannot move outwards. On suitable increase in speed the valve piston 8 moves to to outer position asalready described. The balls 49 can now be moved to engage the groove 55 so that the valve piston 9 is now able to move out when itssuitable speed is reached. In this position, i. e. with both piston 18 and 9 in their outer positions, if the balls 49 are positioned in the groove 5!) the piston 8 cannot move inwards until after ethe'piston a has assumed its inner position. With the piston 3 in the outer positionythe oil pressure is led to diaphragm l8 and dia hragm 19 is open to exhaust through the groove 41 in the piston 9. If the valve member 9 moves to the outer position, the groove 41 now positions opposite to the duct 24 and the duct 45 is closed. Pressure, therefore, reaches both diaphragms I8 and. I9 through ducts I55, 24, the ball 53 and spring 52 operating in a similar manner to ball 36 and spring 40.

Also mounted in the rotary housing part H2 are valves having piston members 54, 55. The bore of the valve 54 connects with the diaphragm 18 by means of one or more ducts 56 and the bore of the valve 55 connects with the diaphragm 19 by means of similar ducts 51. Oil pressure from the diaphragms can, therefore, act on the outer ends of these piston members. Exhaust ports 53 are provided for each valve. 54 and 55. Springs 59, 60, press the valve rpiston members inwardly and below some given speed the springs 59, B5, are able to overcome the centrifugal force on the valve piston members so that they move inwards and uncover the exhaust ports 58. This allows any pressure in the diaphragm spaces to escape. At low speeds, therefore, the clutches 15, ll, are automatically disengaged owing to the valves 54, 55 being in the inner positions, but if speed is increased the centrifugal force on the valve pistons is first sufficient to overcome the force from the springs and then the oil pressure Which also acts on the outer ends of the pistons.- During initial increase in speed from idling condition, the pressure in the system is kept at suitable values, dependent on R. P. M., owing to the fact that this is determined by the centrifugal force on the valves. Spaces at the inner end of the valves are provided with small openings BI and these spaces are connected by ducts 62 and small rotary valve 63 to the delivery of the pump 29. The valve 63 may be connected to a footpedal or hand lever. If the valve 63 is shut the action of the valves is dependent only on the centrifugal force on the valve, but if the rotary valve 53 is opened, some of the pressure from the pump willreach the spaces and this pressure will add to the centrifugal force, thus causing the valves to open and shut at lower R. P. M. With the valve 63 in a more or less open position the delivery of fluid will more or less overcome the exhaust through El and, therefore, provide a varying pressure in the spaces. Hence, by movement'of'the valve the speed at which the clutches engage can be varied.

As shown in Figure 4, a similar arrangement can be provided at the outer or inner ends of valves 8, 9. If, for example, there are no holes 48 and the exhaust from duct 24 is taken through an exhaust port 49a similar to I49 and a small opening 61a is provided in place of holes 48 and the duct 52 led to the spaces at the outer ends of valves 8 and 9, an additional force, depending more or less on the opening of the rotary valve 63, will then act on the outer ends of the valves 9, 9 so that the speed at which theseoperate can be varied according to the position of the rotary valve. This will however not affect any substantial variation of the relationship between the difference in speed required to operate the valves inwards and outwards and the difference in speed of the rotary housing brought about by the change in driving ratios. I Some oil from the pump 29 is allowed'to reach the'faces of the disengaged clutch surfaces, via duct 22. This together with a suitably sized duct 24 and the necessary range of pressures from pump 29, provides inherently progressiv engagement. The oil on the faces cannot be removed and thus permit positive engagement without relative rotation and progressive action.

The operation of the apparatus described is as follows: i

At low speeds the valves 8, 9, '54, 55 will be in the inner positions. on speeding up the input shaft II], the valves 54, 55, will move to the outer positions and fluid pressure will act on the diaphragm l9 and engage the clutch l1, so that power is transmitted through the shaft 30 and gearwheels 35, 31, 4|, 42, to the output shaft 29. On suitable increase in speed, valve 8 moves out wards thereby exhausting pressure from the diaphragm l9 and applying pressure to the diaphragm 18 so that the clutch I6 is engaged and power then passes via the cage 25 to both shafts 29, 30. The speed of the input shaft may fall on changing from one ratio to the next, but the valve 8 will not move inwards unless there is some considerable decrease in speed, because of the action of the ball 36 and spring 49.

On again increasing the speed of the input shaft, the valve 9 will move outwards and both clutches IE, IT, will be engaged. This will have the effect of locking the shafts 29, 30, together and the power will pass via the shaft 29, the gearwheel 42 freewheeling through the clutch 39. Similarly, if speed falls, valve 9 will first move inwards, causing clutch Hi to operate alone and as described. This may allow the input shaft to increase in speed, but the valve 9 would remain inwards unless there is some predetermined; increase in speed, because of the action of spring 52 and ball 53.

If the arrangement includes a pressure varying device operating at the outer ends of valves 8, 9, then the speeds at which the changes occur can be varied, or a change caused when desired within certain limits of speed by variation of the position of rotary valve 53.

The apparatus, as shown with the variable pressure control to the inner ends of valves 54, 55, is suitable for a battery electric vehicle, although the rotary housing H is shown in the form of an engine flywheel.

Ducts similar to 92 may lead from a valve sim ilar to 93 to the inner ends of the valves 8, 9.

Variation of pressure in this space by means of bleed holes such as 6! and a va1ve 63 will cause the speeds of operation of the valves to be varied.

To ensure rapid and complete emptying of the diaphragm spaces when required, the exhaust ports are associated therewith and channels which connect the ports to said spaces, and some parts or the whole of the ports and channels at each position along their whole length are located further from the axis of the rotary part than the outermost parts of said spaces.

The invention can be applied to internal combustion engine driven vehicles, battery electric vehicles, and other apparatus.

I claim:

1. A power transmission apparatus comprising a first rotary member, at least two hydraulically operated clutch engaging rings carried by said first rotating member, a second and a third rotary member, clutch members secured to each of the said second and third rotary members, said clutch engaging rings hydraulically engageable with the said clutch members, the first rotarymember having spaces for receiving fluid under pressure for actuating said rings, at least enemas;

7 one valve device carried-by first rotary'memher, valve piston in said device, spring means for holding said piston inwardly and yielding outwardly by centrifugal force, a spring Pressed element carried by said first rotary member and noting said valve piston to locate it in posh tie s at the ends of its travel, said valve device ng'ports which are controlled by said piston .fd g and exhausting the said fluid spaces as clutches engaged or piston is located in each of its two positions. 2. A power transmission apparatus comprising .a first rotary member, at least two hydraulically operated clutch engaging rings carried by said first rotating member, a second :and a third rotary Them-her, clutch members secured to ;each of *thesaid second and third rotary zmembers, .sa'id clutch engaging rings hydraulically engage- :able with the said clutch members, the first rotary member having spaces for receiving fluid under pressure for actuating said rings, at least one valve device carried by said first rotary member, a valve piston in said device, spring means for holding said piston inwardly and yielding :outwardly by centrifugal force, a spring pressed element carried by said first rotary member and detents on said valve'piston engageable with the :spring pressed element to locate the piston in positions at the ends of its travel, said valve device having ports which are controlled by said piston for filling and exhausting the said fluid spaces whereby the clutches are engaged or disengaged when said piston is located in each of its two positions, the weight of the piston and the resistance of the spring means and the resistance against movement of the piston provided by the spring pressed element and the detent being so selected that (l) the piston moves out at a predetermined speed of the first rotary member greater than the speed of said member :at which the piston moves inward and (2) the difference in speed required for outward and inward movements respectively of the piston is greater than the difierence in speeds of said first rotary member caused by a change in transmission ratio.

3. A power transmission apparatus comprising a first rotary member, at least two hydraulically operated clutch engaging rings carried by said first rotating member, a second and a third rotary member, clutch members secured to each of the said second and third rotary members, said clutch engaging rings hydraulically engageable with the said clutch members, the first rotary member having spaces for receiving fluid under pressure for actuating said rings, at least one valve device carried by said first rotary member, a valve piston in said device, spring means for holding said piston inwardly and yielding outwardly by centrifugal force, a spring pressed element carried by said first rotary member and acting on said valve piston to locate it in positions at the ends of its travel, said valve device having ports which are controlled by said piston for filling and exhausting the said fiuid spaces whereby the clutches are engaged or disengaged when said piston is located in each of its two positions, and means for varying the fluid pressure acting on the exposed area of the valve piston whereby the operator can vary the operationlof the valve device to cause it to efiect a change of driving ratio at a different speed of the first rotary member.

4. A power transmission apparatus comprising a :first rotary member, at least two hydraulically operated clutch engaging rings carried by-said first rotating member, a second and :athird rotary member, clutch members secured to each of the said second and third rotary members, said clutch engaging rings hydraulically engageable with the said clutch members, the first rotary member havin spaces for receiving ,fiuidxunder pressure for actuatin said rings, at leaston'e valve device carried by said first rotary member, a valve piston in said device, spring means for holding said piston inwardly and yielding outwardly by centrifugal force, a spring pressed element carried by said first rotary member and-"detents on said valve pistcn-engageable with the spring pressed element-to locate the piston ,in positions at the ends of its travel, said valve device having ports which are controlled by said piston for filling and exhausting the said fluid spaces whereby the clutches are engaged or disengaged when said piston is located in each of its two positions, the weight of the piston and the :resistance of the spring means and the resistance against movement of the piston provided by the spring pressed element and the detent being so selected that (1) the piston moves out at apredetermined speed of the first rotary member greater than the speed of said member at which the piston moves inward and (2') the difference in speed required for outward and inward movements respectively of the piston is greater than the difierence in speeds of said first-rotary-member caused by a change in transmission ratio, and means for varying the fiuid pressure acting on the exposed area of th valve piston whereby the operator can vary the operation of the valve device to cause it to effect a ;change of driving ratio at a different speed but without substantially varying the relationship between said speed dif ferences.

5. A power transmission apparatus comprising a first rotary member, at least two hydraulically operated clutch engagingrings carried by said first rotating member, a second and a third rotary member, clutch members secured to each of the said second-and third rotary'members, said clutch engaging rings hydraulically engageable with the said clutch members, the first rotary member having spaces'for receivin fluid under pressure for actuating said rings, a valve device carried by said first rotary member, two adjacent bores in said valve device, a piston located in each bore, one of which is associated with ports through which hydraulic pressure can be supplied in'engaging one clutch at a time and another clutch at another time and the two of which are associated with ports through which hydraulic pressure can be supplied to one of the clutchesat another time to enable pressure to be supplied to apply both clutches together, spring means for holding said pistons inwardly and yielding outwardly by centrifugal force, and spring pressed elements carried by the first rotary member. and acting on said valve pistons to locate themin positions at the ends of their travel.

6. A power transmission apparatus comprising a first rotary member, at least two hydraulically operated clutch engaging rings carried by said firrt rotating member, a second and a third rotary member, clutch members secured to each of the said second and third rotary members, said clutch engaging rings hydraulically engageable with the said clutch members, the first rotary member having spaces for receiving fluid under pressure for actuating said rings, a valve device carried by said first rotary member, two adjacent bores in said valve device, a piston located in each bore, one of which is associated with ports through which hydraulic pressure can be supplied in engaging one clutch at a time and another clutch at another time and the two of which are associated with ports through which hydraulic pressure can be supplied to one of the clutches at another time to enable pressure to be supplied to apply both clutches together, spring means for holding said pistons inwardly and yielding outwardly by centrifugal force, spring pressed elements carried by the first rotary member and acting on said valve pistons to locate them in positions at the ends of their travel, and interlocking means between the valve pistons whereby one piston can only move inwardly or outwardly when the other is in a selected position, i. e. either inwards or outwards.

7. A power transmission apparatus comprising a first rotary member, at least two hydraulically operated clutch engaging rings carried by said first rotating member, a second and a third rotary member, clutch members secured to each of the said second and third rotary members, said clutch engaging rings hydraulically engageable with the said clutch members, the first rotary member having spaces for receiving fluid under pressure for actuating said rings, at least one .valve device carried by said first rotary memher, a valve piston in said device, spring means for holding said piston inwardly and yielding outwardly by centrifugal force, a spring pressed element carried by said first rotary member and acting on said valve piston to locate it in positions at the ends of its travel, said valve device having ports which are controlled by said piston for filling and exhausting the said fiuid spaces whereby the clutches are engaged or disengaged when said piston is located in each of its two positions, and a pressure operated valve means for controlling the fluid pressure to one or more of the ports and ducts controlled by the valve piston whereby the valve piston opens pressure to or releases pressure from the pressure operated valve means, which means operates to open pressure to or release fluid from the said space.

8. A power transmission apparatus comprising a first rotary member, at least two hydraulically operated clutch engaging rings carried by said first rotating member, a second and a third rotary member, clutch members secured to each of the said second and third rotary members, said clutch engaging rings hyraulically engageable with the said clutch members, the first rotary member having spaces for receiving fluid under pressure for actuating said rings, a valve device carried by said first rotary member, two adjacent bores in said valve device, a piston located in each bore, one of which is associated with ports through which hydraulic pressure can be supplied in engaging one clutch at a time and another clutch at another time and the two of which are associated with ports through which hydraulic pressure can be supplied to one of the clutches at another time to enable pressure to be supplied to apply both clutches together, spring means for holding said pistons inwardly and yielding outwardly by centrifugal force, and spring pressed elements carried by the first rotary member and detents on said valve pistons engageable with the spring pressed elements to locate the pistons at the ends of their travel, the weight providing the centrifugal force on the pistons and the strength of the spring means and the resistance against movement of the piston provided by the spring pressed element and the detent being so selected that (1) each piston moves out at a predetermined speed of the first rotary member greater than the speed of said member at which the piston moves inward and (2) the difference in speed required for outward and inward movements respectively of the piston is greater than the difference in speeds of said first rotary member caused by a change in transmission ratio.

9. A power transmission apparatus co:mprising a first rotary member, at least two hydraulically operated clutch engaging rings carried by said first rotating member, a second and a third rotary member, clutch members secured to each of the said second and third rotary members, said clutch engaging rings hydraulically engageable with the said clutch members, the first rotary member having spaces for receiving fluid under pressure for actuating said rings, a valve device carried by said first rotary member, two adjacent bores in said valve device, a piston located in each. bore, one of which is associated with ports through which hydraulic pressure can be supplied in engaging one clutch at a time and another clutch at another time and the two of which are associated with ports through which hydraulic pressure can be supplied to one of the clutches at another time to enable pressure to be supplied to apply both clutches together, spring means for holding said pistons inwardly and yielding outwardly by centrifugal force, and sp ing pressed elements carried by the first rotary member and detents on said valve pistons engageable with the spring pressed elements to locate the pistons at the ends of their travel, the weight providing the centrifugal force on the pistons and the strength of the spring means and the resistance against movement of the piston provided by the spring pressed element and the detent being so selected that ('1) each piston moves out at a predetermined speed of the first rotary member greater than the speed of said member at which the piston moves inward and (2) the difference in speed required for outward and inward movements respectively of the piston is greater than the difference in speeds of said first rotary member caused by a change in transmission ratio, and means for varying the fluid pressure acting on the exposed area of the valve piston whereby the operator can vary the operation of the valve device to cause it to effect a change of driving ratio at a difierent speed but without substantially varying the relationship between said speed differences.

HOWARD FREDERICK HOBBS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Num er Name Date 2,075,404 Nika Mar. 30, 1937 2,386,217 Kegresse Oct. 9, 1945 

